Gogobot - This travel guide delivers personalized recommendations for places to visit based on user experience. For example, if you're planning a stag party with five friends, you will receive a completely different set of recommendations from those preparing for a family vacation. It recently received a substantial update and is highly regarded in the android community.

Locish - Another travel companion which aims to offer a similar targeted experience as Gogobot, providing specific advice tailored to each user. It also has a feature that let's you ask questions in real time, like "what is the best jazz bar to visit in paris?" where other users can reply straight away.

TripIt - For those constantly making notes of train times and flight schedules, TripIt is for you. TripIt collates information your email inbox to create a convenient itinerary of your travels and also offers weather, maps and directions. It's got a ton of accolades and well worth checking out. (If you're okay with it accessing your email acount!)

Kayak – Travel search engine for hotels, flights and car-hire. It aggregates a whole host of airline and booking companies to ensure the prices are always competitive. I always check this first before booking any flight.

I personally use TripAdvisor on my trips. I really like the fact that you can use them offline, and that there are individual city apps to install. For example, the Prague TripAdvisor app brought me around the entire city, and I was able to see all the most important stuff within one or two days It was great! Here is the catalogue for all the cities: City Guides Catalog

Triposo is also great, we wrote a review about it not too long ago when Kris used it for the Mobile World Congress 2014 in Barcelona.